Comparison of pressure treatment and heat treatment of skim milk with added starch on subsequent acid gelation of milk

Milk, naturally contaminated with aflatoxin M1 (AFM1) was separated with a hand-operated separator. Distribution of AFM1 paralleled the partitioning of whole milk into cream and skim milk. Most of the whole milk was recovered as skim milk, which also contained most of the AFM1. Cream accounted for 5–15% of the amount of whole milk and had 2–14% of AFM1 that originally occurred in whole milk. Cream and skim milk were pasteurized at 64°C for 30 min, AFM1 was stable in both products given this heat treatment.

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Inactivation of Yersinia pseudotuberculosis 197 and Francisella tularensis LVS in Beverages by High Pressure Processing

Journal of Food Protection ◽

10.4315/0362-028x-72.1.165 ◽

2009 ◽

Vol 72 (1) ◽

pp. 165-168 ◽

Cited By ~ 3

Author(s):

JOSEPH E. SCHLESSER ◽

BRIAN PARISI

Keyword(s):

High Pressure ◽

Francisella Tularensis ◽

Orange Juice ◽

Yersinia Pseudotuberculosis ◽

Hold Time ◽

Skim Milk ◽

High Pressure Processing ◽

Pressure Treatment ◽

Log Reduction ◽

Pressure Resistance

In 2003, the U.S. Department of Health and Human Services announced a new research program to develop technologies and strategies to prevent and minimize potential food safety and security threats. The threat of terrorist attacks against the nation's food supplies has created the need to study microorganisms not typically associated with foodborne illness. High-pressure processing has been proposed as a treatment to reduce Yersinia pestis and Francisella tularensis LVS levels in beverages. The objectives of this work were to determine the pressure resistance of Y. pseudotuberculosis 197 (surrogate for Y. pestis) and F. tularensis LVS (vaccine strain). For each bacterium, samples of ultrahigh-temperature pasteurized skim milk and pasteurized reduced-acid orange juice (pH ca. 4.2) were inoculated at a minimum level of 5 log CFU/ml. Ten-milliliter samples of the inoculated product were vacuum sealed in polyester pouches and subjected to pressures of 300 and 500 MPa for holding times ranging from 30 s to 6 min. One set of trials was performed at an initial temperature of 10°C and another at 25°C. Processed samples were immediately plated and enumerated. A pressure treatment of 300 MPa at 25°C for less than 6 min was not sufficient to achieve a 5-log reduction of Y. pseudotuberculosis 197 or F. tularensis LVS in milk. However, a pressure treatment of 500 MPa was effective at hold times as low as 30 s. Overall, F. tularensis LVS demonstrated less pressure resistance than Y. pseudotuberculosis 197. Based on these findings, a high-pressure process designed to inactivate 5 log CFU of Y. pseudotuberculosis 197 per ml and F. tularensis LVS in orange juice or milk should be set at or above 500 MPa with a hold time of 2 min or greater.

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Heat Resistance of Escherichia coli in Cow and Buffalo Milk

Journal of Food Protection ◽

10.4315/0362-028x-43.5.376 ◽

1980 ◽

Vol 43 (5) ◽

pp. 376-380 ◽

Cited By ~ 2

Author(s):

R. S. SINGH ◽

B. RANGANATHAN

Keyword(s):

Escherichia Coli ◽

Heat Treatment ◽

Heat Resistance ◽

Skim Milk ◽

Buffalo Milk ◽

Time Interval ◽

E Coli ◽

Heat Resistant ◽

Whole Milk

Three Escherichia coli cultures (0111:B4, 0127:B8 and NP) were selected to study their heat-resistant characteristics when in cow skim, cow whole and buffalo whole milk. The temperatures of heat-treatment included in this study were 50, 55, 60 and 63 C. The time interval during heat-treatment was 10 min at 50 and 55 C and 5 min at 60 and 63 C. Marked differences in heat-resistance were observed in the three E. coli cultures. The z-values obtained for strain 0111:B4 were 8.3, 9.0 and 10.2 when tested in cow skim milk, cow whole milk and buffalo milk, respectively. The z-values for 0127:B8 and NP were 17.5, 18.0 and 19.2 and 18.8, 19.0 and 20.3, respectively, for the three types of milk.

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The influence of milk composition on pH and calcium activity measured in situ during heat treatment of reconstituted skim milk

Journal of Dairy Research ◽

10.1017/s0022029910000026 ◽

2010 ◽

Vol 77 (3) ◽

pp. 257-264 ◽

Cited By ~ 28

Author(s):

Jayani Chandrapala ◽

Ian McKinnon ◽

Mary Ann Augustin ◽

Punsandani Udabage

Keyword(s):

Heat Treatment ◽

High Temperatures ◽

Skim Milk ◽

Milk Composition ◽

Complexing Agents ◽

Calcium Activity ◽

Initial Ph ◽

Ph Decrease ◽

Milk Solids

The pH and calcium activity of reconstituted skim milk solutions (9–21% w/w milk solids non-fat) on heating and after cooling were studied as a function of milk pH prior to heating (pH 6·2–7·2 at 25°C) and added calcium complexing agents (phosphate or EDTA). The pH decreased as the temperature was raised from 25 to 90°C and the magnitude of the pH decrease was greater with increase in initial pH at 25°C before heating or milk concentration. The pH decrease on heating from 25 to 90°C in skim milk solutions with added calcium complexing agents was lower than that of milk without the addition of these salts. The calcium activity decreased on heating from 25 to 60°C. The magnitude of the change decreased with increase in initial pH at 25°C before heating and milk concentration. The decrease in calcium activity on heating from 25 to 60°C for skim milk solutions with added calcium complexing agents was lower than that of milk solutions without the addition of calcium complexing agents. The changes in pH and calcium activity on heating milk were largely reversible after cooling the milk. The results suggested that the pH and calcium activity at high temperatures are a function of the milk composition. Knowledge of the initial pH prior to heating alone is not sufficient for predicting the changes that occur during heating.

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